In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. An over the wire (OTW) catheter is advanced over the guide wire to the treatment site. The medical device is then expanded to reopen the artery. The OTW catheter may have a guide wire lumen which is as long as the catheter or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter and enters the catheter at the distal portion. Alternatively, a fixed wire balloon may be used. This device features a guide wire which is affixed to the catheter and cannot be removed. Such procedures and catheters are well known.
To help prevent arterial closure, repair dissection, or prevent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is pulled back to expose the stent. After the sheath is removed, the stent is free to expand or be expanded. In order to remove the retaining sheath which contains the stent, devices such as pull back means are utilized such that the physician may controllably retract the sleeve from the proximal end to release the medical device. Example of such catheters can be found in U.S. Pat. Nos. 5,534,007, 5,360,401 and 5,571,135, all of which are herein incorporated by reference in their entirety.
Dilation catheters generally have been recently made to have low profiles with stiffer proximal shafts while maintaining flexible distal shafts. A stiffened proximal shaft provides greater push to the catheter which facilitates advancement over a guidewire in the tortuous anatomy. It is also found to be important with stent delivery systems is to have an material which has as close to a one to one force ratio as possible such that the physician may accurately locate the stent within the target area with out any additional "play" in the catheter due to the flexibility of the overall shaft. Stiffened proximal shaft section formed of plastic materials, stainless steel and superelastic NiTi alloys are disclosed in the prior art. However, the raw material and manufacturing costs for a catheter having a relatively stiff proximal shaft is high. The present invention provides an intraluminal catheter which has a low profile and a relatively stiff proximal shaft which has an improved force ratio which is easy and inexpensive to manufacture.
A typical catheter utilizing pull back means has a proximal shaft housing a guidewire lumen and a free floating pull back wire with no separate track or lumen. A further problem found with stent delivery catheters utilizing a pull back means and a guide wire, as mentioned above, is that during manufacturing and/or the tortuous feeding of the catheter through the body, the pull back wire and the guide wire, and/or guide wire lumen, tend to get tangled with each other causing a recoiled spring phenomenon (scrunching or a choke collar type effect) in the catheter and/or a jumping forward of the distal end of the catheter when the retaining means is retracted to release the medical device. The present invention eliminates interaction between the wires and serves to solve this problem as well.
Related prior art of interest include U.S. Pat. Nos. 5,480,383, 5,549,552, 5,499,973, 5,545,138, 5,605,543 and 5,554,121, all of which are herein incorporated by reference in their entirety.